An international team of scientists has computationally pieced together a likely genome for the common ancestor of mammals by working backward from 32 genomes of living species.
The researchers reconstructed the complete set of chromosomes at 16 nodes stretching back to the common ancestor of all mammals.
Fossils found in Africa and North America are too specialized to be a common ancestor of all mammals, but they would have lived around the same time as the first mammal species.